The effect deficient of strontium on structural, magnetic and magnetocaloric properties of La_(0.57)Nd_(0.1)Sr_(0.33-x)MnO_3 (x=0.1 and 0.15) manganite

摘要

We have investigated the effect of nominal strontium deficiency on the structure, magnetic and magnetocaloric properties of La_(0.57)Nd_(0.1)Sr_(0.33-x)MnO_3 (x=0.1 and 0.15), [LNS_(0.23)MO and LNS_(0.18)MO] manganese perovskites. The polycrystalline samples have been elaborated by the conventional ceramic method at 1673 K. The refinement of the structure by the Rietveld method revealed that these compounds crystallize in a rhombohedral (R3C) perovskite structure. Magnetization as a function of temperature shows that these compounds exhibit a paramagnetic to ferromagnetic phase transition with decreasing temperature. The ferromagnetic transition temperature (T_c) decreases from 339 K for x=0.1 to nearly the room temperature 315 K for x=0.15 with increasing nominal strontium content. A large magnetic entropy change ｜ΔS_M｜ deduced from isothermal magnetization curves, has been observed in our samples with a peak centered around their respective T_c. The maximum of the magnetic entropy change ｜ΔS_M~(max)｜ in a magnetic field change of 5 T is found to be 4.42, 4.36Jkg~(-1) K~(-1) for x=0.10, 0.15 respectively. The field dependence of the magnetic entropy change is also analyzed showing the power law dependence, ΔS_M∝H~n where n=0.684(1) for x=0.1 and n=0.714(4) for x=0.15 at their respective transition temperatures. Large relative cooling power value of 214Jkg~(-1) is obtained for La_(0.57)Nd_(0.1)-Sr_(0.18)MnO_3 sample, at a field change of 5 T. This relatively large value associated to a curie temperature of 315 K make the present compound a promising candidate for magnetic refrigerators around room temperature.